1. Field of the Invention
The present invention relates to the fields of data networking and digital communication. More specifically, the present invention relates to adaptive or feedback channel equalizers employed in receivers of network interface controllers (NIC) or digital communication terminals.
2. Background Information
Recent advances in microprocessor and communication technology have led to increasing number of computers and other digital devices (such as, printers, scanners and so forth) being networked together. Computers and other digital devices of close proximity to one another are networked together locally through a local area network (LAN), which in turn are networked with other locally networked remote computers/digital devices by internetworking the LANs via wide area networks (WAN).
Notwithstanding the great advances in networking technology, to-date, the popularity and success in networking computers and other digital devices together are still substantially confined to the work place, where the networking environment is typically a well controlled environment (in terms of control attenuation, delay, echo and so forth). Networking computers and peripherals together in the home remains a challenge, as economics dictate that the networking be accomplished in a less controlled environment, using existing power lines or phone lines, as called for by industry initiatives such as the CEBus and Anypoint Networking, and with low cost components.
Typically, computers and digital devices are networked together using network interfaces (also referred to as network from the network interface controllers, NIC for short). Included in each NIC is at least one receiver or transceiver (hereinafter, simply receiver) to receive or recover signals from the networking medium. Most receivers include adaptive channel equalizers (also referred to as feedback channel equalizers), which are used to compensate time variant channel characteristics, to minimize the interference between the symbols of digital signal.
Among the various digital equalizers, decision feedback equalizer is one of the most popular. Prior art decision feedback equalizers are typically constituted with feed forward and feedback sections having similar constructions that are multipliers based. In other words, both sections, feed forward and feedback, are provided with multiple multipliers to correspondingly modify the delayed versions of the equalizer input and output signals respectively.
Multipliers are inherently complex, and therefore account for a large portion of the real estate and cost of a receiver ASIC equipped with such an adaptive or feedback channel equalizer. Thus, an improved decision feedback equalizer that contributes to reducing the cost of receiver ASICs and in turn, the cost of NICs and networking enabled digital devices, is desired.
A novel receiver having a decision feedback equalizer is disclosed. The decision feedback equalizer is equipped with a feedback section to generate a feedback signal. The feedback section includes a plurality of taps to successively delay a filtered version of an input signal of the decision feedback equalizer. The feedback section further includes a plurality of comparators, correspondingly coupled to the taps, to examine the corresponding delayed versions of the filtered input signal to affect the generation of the feedback signal with the examination results.